Egg Tempera on Casein

Koo
I have not tried this. Wehlte and especially Mayer indicate that it is fine. Mayer says that it is easier to control and apply but that it is more brittle. He also writes that the manipulation of egg tempera paint on casein gesso is in some way inferior. I do not know if this means that it makes a coarser gesso or if it is not as absorbent as a well made chalk/gypsum glue ground.

​Koo, I think you may have already tried this with a commercial casein gesso.

First, I want to state here that in the interest of making my responses less wordy in the future, I will be writing animal glue- Ca- ground when I refer to a traditional gypsum-glue ground or a chalk-glue ground.  The Ca- will be a substitute for CaCO3 or CaSO4. I will maintain the verbose “acrylic dispersion ground” terminology in lieu of “acrylic gesso” since the latter really makes no sense and only confuses the situation.
My experience with commercial casein paints on a larger scale (not necessarily those tubed for  fine art purposes, but those in cans for theatrical scene painting) is that they are loaded with ammonia to prevent premature decay. I wonder if the same would be true for some commercial casein “gesso.” Probably it is an apples and oranges situation, but I want to put that out there.
Like tubed “egg tempera,” the fine art casein “gesso” products that I have seen all have a drying oil component added. To my understanding, casein/oil emulsions tend to become quite yellow over time. There may be some way to surmount this in the formulation. No matter what, the handling properties and absorption qualities of said grounds would seem to be different than that of a traditional glue-Ca- ground. I would guess that a simple casein solution-Ca- ground could be prepared that would be rather close to an animal glue-Ca- ground. The ground containing oil may be perfectly suitable and perhaps preferable to traditional grounds for particular medium/effects, but just that it would be different from the traditional product. Additionally, I do know, based on my own meager work on the subject (analysis of the ability to detect proteins extracted from a natural sources using immunology stains) the hydrolyzation ingredients have a major effect on the product and the resultant residues (ie ammonia/ammonia salts vs. borax, vs. etc.)
None of the above really has anything to do with what is best for anyone’s specific needs. When I paint in egg tempera or want to water gild, I require the most absorbent, yet stable, ground possible. Others may prefer a slightly less absorbent ground.  They may be very happy with commercial clay or gesso boards. These are not inferior in any way, just different, and more or less appropriate for specific techniques and effects.

​Thanks for those replies.  You’re correct, George, I did paint on Sinopia’s casein gesso, but as Brian notes, it is a casein product with added oil, not pure casein.  Although Sinopia’s casein gesso is advertised as “ideally” suited to egg tempera, I found the ground insufficiently absorbent for some of my working methods.   
My experience has been that if one works exclusivley in tempera as if “drawing” with the brush (using a well-wiped, finely pointed brush to crosshatch lines), than many grounds with a moderate degree of absorption work well.  But the minute you start doing anything different (“sponging” on paint, as I do; floating ‘petit lacs’; working with a wide, flat watercolor brush; etc) those same grounds do not have enough absorbency, enough places for the water to go; the water remains too present to the paint film, encouarges underlying layers to dissolve, and, even with a very light touch, there is apt to be lifting. 
Interesting that casein/oil products become very yellow over time….more so than regular oil paint?  Do you know why, Brian – does the casein (or added amonia) encourage greater yellowing in the oil?  Or are they poor quality oils?

This student also asked about painting on red bole – I presume with rabbit skin glue as the binder (she didn’t specify).  I would think paint would just sink in?  Don’t know about that one either…

Thanks for continuing the conversation,

Koo

​​Thanks, Nancy – very interesting, I didn’t realize that about casein.